Abstract: We disclose methods of blocking the transmission of COVID-19 and other airborne pathogens between people standing on either side of a door separating an interior space from an exterior space. In a preferred embodiment, the method comprises hingedly mounting a rigid transparent gate directly to the door so that the gate swings independently of the door. Preferably, the gate is dimensioned to substantially fill the width defined by the frame holding the door. The method further comprises releasing the gate from a storage position against the door, coupling the gate to the door frame and opening the door.